It will be appreciated that due to capacity and other problems with respect to the internet, internet connections are often lost during the transfer of files from sender to receiver or, alternatively, from server to client. This type of interruption is exceedingly annoying due to the fact that a large amount of the information may have already been transmitted at the time of the interruption. Current systems do not allow for the transmission of only information that occurred after the interruption, but rather require that the entire file be transferred from its beginning. In the past, information transfer from sender to receiver over the internet was accomplished in blocks or packets of information. The blocks were not transferred with interrupted links in mind, but were rather coded with information for flow control to accommodate bandwidth limitations or usable bandwidth associated with capacity of network switches to store and transmit data. Flow control systems have been utilized both in synchronous and asynchronous systems to be able to accommodate switches and to recognize when buffer space, either at a switch or at the recipient, was incapable of responding adequately to the inflow of information.
In the case of the transfer of large files such as MPEG or JPEG in which images are to be transmitted from the sender to receiver, interruption of the link may result in the necessity of transmitting the entire image. Depending on the size of the image and its complexity, it may take 18 to 20 minutes to be able to transfer the file to the receive side. If the interruption occurs close to the end of the transmission, it would be convenient to be able to restart the transmission and not have to transmit data that has already been received.
The problem is exceedingly severe in the transmission of video images. It is desirable, bandwidth available, to be able to transmit realtime video across the internet. However, due to bandwidth limitations, this is neither practical now nor in the future for high quality video transmission to be transmitted on a real-time basis. As a result, it takes long periods of time to transmit video images. As a result, the loss of a link during a video transmission results in a major disruption at the receive side, with the interruption causing more problems than the limited bandwidth of the network due to the requirement of restarting the entire process during a communications outage. Moreover, due to the increasing usage of the internet, oftentimes with multiple users, the amount of interruption increases. For a single server serving as many as 200-500 clients, interruptions are frequent, with there being no convenient way, presently, to overcome the restart problem.
Moreover, for those systems in which the client side can interrupt the server side upon sensing of excessive load, this constitutes an interruption which nonetheless must be compensated for when it is appropriate to reestablish the connection.
One such client-side interruption system is described in U.S. patent application Ser. No. 08/755,029, filed by Hiroshi Kobata on Nov. 22, 1996. Here, a system for regulating the time of transmission of information from a server to a client is described in which network occupation is sensed and the transmission is caused to cease when insufficient bandwidth is available. Whether the interruption of a large file is caused by sensing network overload by the particular client or server, or whether it is due to network breakdowns, the problem is still the same. Large files must be restarted from the beginning.